| Document And Entity Information | Aug. 15, 2022 |
| Document Information [Line Items] | |
| Entity, Registrant Name | ARCH THERAPEUTICS, INC. |
| Document, Type | 8-K/A |
| Document, Period End Date | Aug. 15, 2022 |
| Entity, Incorporation, State or Country Code | NV |
| Entity, File Number | 000-54986 |
| Entity, Tax Identification Number | 46-0524102 |
| Entity, Address, Address Line One | 235 Walnut Street |
| Entity, Address, Address Line Two | Suite 6 |
| Entity, Address, City or Town | Framingham |
| Entity, Address, State or Province | MA |
| Entity, Address, Postal Zip Code | 01702 |
| City Area Code | 617 |
| Local Phone Number | 431-2313 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity, Emerging Growth Company | false |
| Current Fiscal Year End Date | --09-30 |
| Amendment Description | 8-K/A (Bylaws 8K Correct) 5.03 9.01 |
| Amendment Flag | true |
| Entity, Central Index Key | 0001537561 |
